A5030468546- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- High-pressure geophysics and materials
- Astronomical Observations and Instrumentation
- Phase Equilibria and Thermodynamics
- Chemical Thermodynamics and Molecular Structure
- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Space Exploration and Technology
- Astrophysical Phenomena and Observations
- Spacecraft Design and Technology
- Superconducting and THz Device Technology
- Planetary Science and Exploration
- Pulsars and Gravitational Waves Research
- Advanced Combustion Engine Technologies
- Thermodynamic properties of mixtures
- Geophysics and Gravity Measurements
- Earthquake Detection and Analysis
- Isotope Analysis in Ecology
Tartu Observatory
2020-2024
University of Tartu
2020-2024
University College London
2020-2024
University of Cambridge
2016-2022
University College Lahore
2021
Leiden University
2013-2018
Leiden Observatory
2013-2017
University of Amsterdam
2009-2016
Max Planck Society
2015
Max Planck Institute for Radio Astronomy
2015
Aims. In this paper the calibration and in-orbit performance of Heterodyne Instrument for Far-Infrared (HIFI) is described.
The composition of giant planets is imprinted by their migration history and the compositional structure hosting disks. Studies in recent literature investigate how abundances C O can constrain formation pathways forming within few tens au from star. New ALMA observations, however, suggest planet-forming regions possibly extending to hundreds au. We explore implications these wider environments through n-body simulations growing migrating embedded planetesimal disks, coupled with a model...
The precise location of the water ice condensation front ('snow line') in protosolar nebula has been a debate for long time. Its importance stems from expected substantial jump abundance solids beyond snow line, which is conducive to planet formation, and higher stickiness collisions ice-coated dust grains, may help process coagulation formation planetesimals. In an optically thin nebula, line easily calculated be around 3 AU. However, its first 5 10 million years, solar was thick, implying...
Formamide (NH2CHO) has been proposed as a pre-biotic precursor with key role in the emergence of life on Earth. While this molecule observed space, most its detections correspond to high-mass star-forming regions. Motivated by lack investigation low-mass regime, we searched for formamide, well isocyanic acid (HNCO), 10 low- and intermediate-mass pre-stellar protostellar objects. The present work is part IRAM Large Programme ASAI (Astrochemical Surveys At IRAM), which makes use unbiased...
ABSTRACT The first detection of gas-phase methanol in a protoplanetary disk (TW Hya) is presented. In addition to being one the largest molecules detected disks date, also organic molecule with an unambiguous ice chemistry origin. stacked emission, as observed Atacama Large Millimeter/submillimeter Array, spectrally resolved and across six velocity channels ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>></mml:mo> <mml:mn>3</mml:mn>...
The composition of planetary solids and gases is largely rooted in the processing volatile elements protoplanetary disks. To shed light on key processes, we carry out a comparative analysis gas-phase carbon abundance two systems with similar age disk mass, but different central stars: HD 100546 TW Hya. We combine our recent detections C$^{0}$ these disks observations other reservoirs (CO, C$^{+}$, C$_{2}$H) gas mass warm tracers (HD, O$^{0}$), as well spatially resolved ALMA spectral energy...
Around 2% of all A stars have photospheres depleted in refractory elements. This is hypothesized to arise from a preferential accretion gas rather than dust, but the specific processes and origin material -- circum- or interstellar are not known. The same depletion seen 30% young, disk-hosting Herbig Ae/Be stars. We investigate whether chemical peculiarity originates circumstellar disk. Using sample systems for which both stellar abundances protoplanetary disk structure known, we find that...
Abstract We present high-resolution millimeter continuum imaging of the disk surrounding young star CI Tau, a system hosting first hot Jupiter candidate in protoplanetary system. The has extended mm emission on which are superposed three prominent annular gaps at radii ∼13, 39, and 100 au. argue that these most likely to be generated by massive planets so that, including Jupiter, contains four gas giant an age only 2 Myr. Two new similarly located those inferred famous HL Tau disk;...
Abstract We have conducted a survey of 328 protostars in the Orion molecular clouds with Atacama Large Millimeter/submillimeter Array at 0.87 mm resolution ∼0.″1 (40 au), including observations Very 9 toward 148 ∼0.″08 (32 au). This is largest multiwavelength this by an order magnitude. use dust continuum emission and to measure disk radii masses Class 0, I, flat-spectrum protostars, characterizing evolution these properties protostellar phase. The mean for are <?CDATA...
Abstract The Atacama Large Millimeter/submillimeter Array (ALMA) can probe the molecular content of planet-forming disks with unprecedented sensitivity. These observations allow us to build up an inventory volatiles available for forming planets and comets. Herbig Ae transition are fruitful targets due thermal sublimation complex organic molecules (COMs) likely H 2 O-rich ices in these disks. IRS 48 disk shows a particularly rich chemistry that be directly linked its asymmetric dust trap....
Abstract Observations of disks with the Atacama Large Millimeter/submillimeter Array (ALMA) allow us to map chemical makeup nearby protoplanetary unprecedented spatial resolution and sensitivity. The typical outer Class II disk observed ALMA is one an elevated C/O ratio a lack oxygen-bearing complex organic molecules, but there are now some interesting exceptions: three transition around Herbig Ae stars all show oxygen-rich gas traced via unique detections molecules SO CH 3 OH. We present...
High resolution line spectra of star-forming regions are mines information: they provide unique clues to reconstruct the chemical, dynamical, and physical structure observed source. We present first results from <i>Herschel<i/> key project "Chemical <i>HErschel<i/> Surveys Star forming regions", CHESS. report discuss observations towards five CHESS targets, one outflow shock spot four protostars with luminosities bewteen 20 2 × 10<sup>5<sup/> : L1157-B1, IRAS 16293-2422, OMC2-FIR4, AFGL...
The inner boundary of protoplanetary discs is structured by the dramatic opacity changes at transition from dust-containing to a dust-free zone. This paper explores variety and limits rim structures in passively heated dusty discs. For this study, we implemented detailed sublimation physics fast Monte Carlo radiative transfer code. We show that not an infinitely sharp wall but diffuse region which may be narrow or wide. Furthermore, high surface densities large silicate grains as well iron...
We present the first results of unbiased survey L1157-B1 bow shock, obtained with HIFI in framework key program Chemical <i>HErschel<i/> Survey Star forming regions (CHESS). The L1157 outflow is driven by a low-mass Class 0 protostar and considered prototype so-called chemically active outflows. bright blue-shifted shock B1 ideal laboratory for studying link between hot (~1000–2000 K) component traced H<sub>2<sub/> IR-emission cold (~10–20 swept-up material. main aim to trace warm gas...
We report the first detection of chloronium, H$_2$Cl$^+$, in interstellar medium, using HIFI instrument aboard \emph{Herschel} Space Observatory. The $2_{12}-1_{01}$ lines ortho-H$_2^{35}$Cl$^+$ and ortho-H$_2^{37}$Cl$^+$ are detected absorption towards NGC~6334I, $1_{11}-0_{00}$ transition para-H$_2^{35}$Cl$^+$ is NGC~6334I Sgr~B2(S). H$_2$Cl$^+$ column densities compared to those chemically-related species HCl. derived HCl/H$_2$Cl$^+$ density ratios, $\sim$1--10, within range predicted by...
Context. Protoplanetary disks around young stars are the sites of planet formation. While dust mass can be estimated using standard methods, determining gas – and thus amount material available to form giant planets has proven very difficult. Hydrogen deuteride (HD) is a promising alternative commonly used tracer, carbon monoxide. However, potential HD not yet been investigated with models incorporating both CO isotopologue-specific chemistry, its sensitivity uncertainties in disk parameters...
Context. Snowlines in protoplanetary disks play an important role planet formation and composition. Since the CO snowline is difficult to observe directly with emission, its location has been inferred several from spatially resolved ALMA observations of DCO+ N2H+.
Despite intensive studies of protoplanetary disks, there is still no reliable way to determine their total mass and surface density distribution, quantities that are crucial for describing both the structure evolution disks up formation planets. The goal this work use less abundant CO isotopologues, whose detection routine ALMA, infer gas disks. Isotope-selective effects need be taken into account in analysis, because they can significantly modify isotopologues line intensities....
There is evidence that the young Sun emitted a high flux of energetic (⩾10 MeV) particles. The collisions these particles with material at inner edge Protosolar Nebula disk induced spallation reactions formed short-lived radionuclei, like 10Be, whose trace now visible in some meteorites. However, it poorly known exactly when this happened, and whether how affected solar system. Here, we present indirect for an ejection protostar, OMC-2 FIR 4, similar to experienced by In case, collide...
High-resolution imaging reveals a large morphological variety of protoplanetary disks. To date, no constraints on their global evolution have been found from this census. An evolutionary classification disks was proposed based IR spectral energy distribution, with the Group I sources showing prominent cold component ascribed to an earlier stage than II. Disk can be constrained comparison different properties. A first attempt disk taxonomy is now possible thanks increasing number...
The gas-solid budget of carbon in protoplanetary disks is related to the composition cores and atmospheres planets forming them. key gas-phase carriers CO, C$^{0}$ C$^{+}$ can now be observed disks. abundance has not yet been well characterized, we aim obtain new constraints on [C]/[H] ratio a sample disks, get an overview strength [CI] warm CO emission. We carried out survey CO$\,6$--$5$ [CI]$\,1$--$0$ $2$--$1$ lines towards $37$ with APEX, supplemented it [CII] data from literature. are...
Abstract The thermal structure of protoplanetary disks is a fundamental characteristic the system that has wide-reaching effects on disk evolution and planet formation. In this study, we constrain 2D TW Hya utilizing images seven CO lines. This includes new ALMA observations 12 J = 2–1 C 18 O as well archival 3–2, 13 3–2 6–5, 6–5. Additionally, reproduce Herschel observation HD 1–0 line flux spectral energy distribution utilize recent quantification radial depletion in Hya. These were...
HD\,139614 is known to be a $\sim$14-Myr-old, possibly pre-main-sequence star in the Sco-Cen OB association Upper Centaurus-Lupus subgroup, with slightly warped circumstellar disc containing ring structures hinting at one or more planets. The star's chemical abundance pattern metal-deficient except for volatile elements, which places it $\lambda$ Boo class and suggests has recently accreted gas-rich but dust-poor material. We identify seven dipole four radial pulsation modes among its...
Molecular line observations are powerful tracers of the physical and chemical conditions across different evolutionary stages star, disk planet formation. Using high angular resolution unprecedented sensitivity Atacama Large Millimeter Array (ALMA) there is now a drive to detect small-scale gas structures in protoplanetary disks that can be attributed directly forming planets. We report ALMA Band 7 sulphur monoxide (SO) nearby planet-hosting around Herbig star HD 100546. SO rarely detected...